1. Field of the Invention
The present invention relates to a tube guide for a column unit, and more particularly to a tube guide for a column unit which can smoothly move a spindle upward and downward by forming a plurality of ribs on the inside surface of the tube guide which guides a spindle which has a multilateral cross-section and which can easily accomplish the broaching.
2. Description of the Prior Art
A well-known column unit applied to a chair has a gas cylinder installed in the interior of a base tube. Namely, a piston rod of a gas cylinder is rotatably installed by a ball bearing to a supporter which seals the lower portion of a base tube. The piston installed at the end of the upper portion of the piston rod is located in the interior of the spindle of the gas cylinder. The interior of the spindle is filled with a pressure gas so as to act as a gas cylinder. The pressure gas in the spindle is not discharged outside even when the spindle is moved upward and downward along the piston. The spindle is separated into upper and lower portion chambers by the piston. A hole is formed in each chamber and the chambers are connected by a bypass channel. A control pin which controls the control valve and the opening/closing is installed in the hole formed in the upper chamber. A sheet of a chair is positioned at the upper portion of the spindle. A chair base which has wheels is installed at the lower portion of the base tube.
The above-mentioned column unit comprises a base tube and a gas spindle. The height of the chair seat is regulated by moving the spindle of the gas cylinder to the upper and lower portions. If the control valve is opened by pressing the control pin when the spindle is located at the lowest portion, the upper and lower chambers of the spindle is connected through the two holes and the bypass channel and the pressure gas of the spindle pushes the piston towards the lower portion of the spindle and the spindle is moved upward along the piston rod. On the contrary, if the force is applied with such a value which exceeds the pressure gas from the upper portion of the spindle, the spindle is moved downward. The height of the chair seat is regulated by regulating such an operation. Further, the cushion is felt when a user is seated on the chair seat due to the gas cylinder.
Such a column unit can be applied to a table. In case the column unit is installed in the table, the table does not need to be rotated and a non-rotating column unit is used and the tube guide has a multilateral, mainly hexagonal inside cross-section. The spindle has a multilateral outside cross-section when the spindle makes contact with the inside. In case a guide sleeve is interposed therebetween to guide the spindle and prevent the rotation of the spindle, the guide sleeve has a multilateral outside cross-section.
The tube guide which has multilateral inside cross-section is manufactured by using a plastic molding die, and the broaching is needed to smoothly move the spindle. However, the broached area is broad and the broaching cannot be easily accomplished due to curved portions.
The present invention has been made to solve the above-mentioned problem, and accordingly it is an object of the present invention to provide a tube guide for a column unit which can smoothly move a spindle upward and downward by forming a plurality of ribs on the inside surface of the tube guide which guides a spindle which has a multilateral cross-section and which can smoothly accomplish the broaching.
In order to achieve the object of the present invention, the present invention provides a tube guide for a column unit which has a multilateral inside cross-section so that the outer cross-section of the column unit can accommodate a multilateral spindle and which is inserted from the upper end portion of a base tube to a predetermined depth, wherein at least one rib which makes contact with the outer surface of the spindle along the axis direction is formed on the inside surface which has a multilateral cross-section of the tube guide.
The rib is formed at a portion except for the bent portion among the inside surfaces of the tube guide.
Two ribs are formed on each surface of the inside surface of the tube guide.
The rib is vertically protruded from the inside surface of the tube guide so that two ribs can make contact with the outer surface of the spindle.
A guide sleeve is installed at the outer surface of the spindle so that the guide sleeve is moved integrally upward and downward and the outside cross-section is multilateral so as to correspond to the cross-section of the inside of the tube guide.
The inside surface of the tube guide has a hexagonal cross-section.
The corner of the cross-section of the inside surface of the tube guide is rounded.